Detection of alloimmune memory cells by chemical modification of the cell surface with mitogenic oxidizing agents
The mitogenic oxidizing agents, neuraminidase and galactose oxidase (NAGO), and sodium periodate (IO-4) were used to induce the differentiation of human alloimmune memory cells. NAGO or IO-4 treatment of peripheral blood mononuclear (PBM) cells obtained from 10 sensitized potential allograft recipients resulted in the induction and augmentation of cytolytic activity to a D locus-defined lymphoblastoid cell panel (B cell panel) and to a HLA-disparate peripheral blood lymphocyte cell panel (PBL cell panel). The acquisition of cytolytic activity was determined in a 4-hr 51Cr release assay. Treatment of in vitro-primed PBM cells (alloimmune memory cells generated in primary long-term mixed lymphocyte cultures) obtained from normal subjects with NAGO or IO-4 also resulted in the induction of specific secondary cytolytic activity. In contrast, NAGO or IO-4 treatment of unprimed PBM cells from normal subjects did not result in the induction of cytolytic activity despite the extensive proliferation induced by such treatment. The strikingly similar results observed with PBM cells from sensitized patients and with in vitro-primed PBM cells suggest that in vivo- and in vitro-generated alloimmune memory cells can be detected by chemical modification of the cell surface induced by NAGO or IO-4. Furthermore, our findings indicate that alloantigen-independent activation of memory cells can be accomplished by treating the memory cells with the mitogenic oxidizing agents.